Body Composition Analysis
Body Composition is the technical term used to describe the different components that, when taken together, make up a person's body weight. When analyzing body composition it is often convenient to think of the body as made of two components: fat and non-fat. The non-fat portion is usually called "fat free mass" or "lean body mass". Your goal is to eliminate the unnecessary fat and/or gain lean mass. Not all fat is bad, in fact some of it is essential. To get a better understanding of just why that is, and what fat we want to eliminate, we need to review a little anatomy and physiology.
You probably realize that the human body is composed of a variety of different tissue types. The so-called 'lean' tissues, such as muscle, bone, and organs are metabolically active, while adipose, or fat tissue, is not. Since scientists like to classify things, they have divided adipose tissue into three different categories:
1. Essential fat, which supports life, and is extremely important to normal bodily function
2. Storage fat, which protects internal organs and supplies some energy requirements
3. Non-essential fat, serves no real purpose and may be detrimental to health
The difference in these tissues is not readily distinguishable by stepping on a scale. A scale simply takes the sum of everything (fat, muscle, water, hair, you name it), and gives an absolute weight measurement. Scales can't determine the lean-to-fat ratio of that weight. An individual can be "over-weight" and not "over-fat." A bodybuilder, for example, may be 8% body fat, yet at two hundred and fifty pounds may be considered "over-weight" by a typical height-weight chart. Therefore, these charts are not a good indication of a person's ideal body weight for optimal health, much less for athletic performance.
In order to identify these tissues, physiologists have developed several different methods of assessing the percent of fat vs. lean mass of an individual. referred to as Body Composition Analysis.
There are many methods of assessment.
Standard for Body Composition Analysis
Body composition analysis through immersion in water has long been the single standard for measuring body fat. Legend has is that Archimedes jumped from his bath naked and ran through the street shouting "Eureka" when he figured out how to determine the mass of an object by using water displacment. You see the king had tasked him with measuring his crown to tell if the goldsmith was cheating him by replacing some of his gold with silver - a metal having less mass and much less expensive. The basic theory hasn't changed since then.
By volume fat weighs less than muscle, and pound for pound fat and muscle each displace a known amount of water, they have a known mass. Basically fat floats and muscle sinks! If you know how much someone weighs, then you can determine how much water they would displace if they were all muscle. Compare that to how much they actually displace, and you can figure out how much of their body composition is fat, and not muscle. (Note: Although we keep using the term "muscle", it's really "fat free mass” or everything but fat).
Isn't it hard to figure out accurately how much water they displace? Well yes, except that you don't measure how much water is displaced exactly, you measure their weight in water, and knowing how much water weighs vs. fat and lean-body-mass, you can figure out the exact amount of body fat.
There are a lot of other methods out there, some of them good, some of them really useless. It's worth noting that whenever anyone describes how accurate their method is, it is always "as compared to hydrostatic". That's right. Every competitor accepts the supposition that hydrostatic body fat measurements are exact and thus they strive to be as close to the hydrostatic measurements as possible. Admittedly, some even come reasonably close, but there is only one standard. Hydrostatic weighing to determine body density, or hydrodensitometry, is the single accepted standard for measuring body fat. And now it's being made available, outside of medical clinics and universities. Why would you use anything else?
A Comparative Methodology Analysis
There's a lot of information out there about the "best" way to test body fat levels. Some of it is valid, some of it shades the truth, and some is outright wrong. It's hard to know what the truth is. Scientific studies abound, and many of them are sponsored by groups with a vested interest in the outcome. In other cases, advertising may extract great 'quotes' from a study that actually indicates the opposite result.
It's confusing. So we'd like to shed a little light on the subject.
Classic Hydrostatic Testing
Classic Hydrostatic TestingUnderwater weighing is the most cumbersome method of body fat testing, but it's also the most accurate. You sit on a scale in a tank of warm water, and then you blow all the air out of your lungs and bend forward until you're completely submerged. You stay submerged for a few seconds while your underwater weight registers on a high precision scale. The result is then plugged into a mathematical equation. This test is repeated and the best results are averaged to get a very accurate reading of the amount of fat in your body.
For many years now, all tests are compared against hydrostatic for the sake of validity and margin of error. Hydrostatic results are considered absolute. In more recent studies, three and four component tests including hydrostatic weighing, bone density testing via DEXA, lung capacity and residual volume testing, and body hydration testing are being used for even greater accuracy. These tests differentiate more components than just fat and lean-body-mass. They account for tissue hydration, and bone density, as well as eliminating error from lung, and intestinal contents which has further proven the validity of basic hydrostatic testing.
Test-retest technical error possibility
Highly technical to derive results
Anxiety, discomfort from being submerged
Subject must follow pre-test guidelines
but...still the best!
Note: The picture at right shows a traditional hydrostatic test that uses a breathing apparatus which we don’t need to use. If for some reason you have had this test done we can use this data in our analysis, however it seldom increases the accuracy of the test.
The New Methodology
Mobile “Body Fat Test” Hydrodensitometry
Put on your bathing suit. Lay down in a tank of warm water. Breathe out. Repeat 3 times. Get out, dry off, and your four page body composition analysis report awaits you!
The Body Fat Test system makes the testing time-efficient, repeatable, and accurate. This test provides the highest level of body fat testing available outside of specialized hospitals, universities and clinics which are often times inaccessible, can take 30 minutes longer to perform and are considerably more expensive. Our system eliminates most of the problems with classic hydrostatic testing and we come to you!
Previous problems that we have solved:
- Expensive? Body Fat Test costs far less than the average clinical test. Our costs average between $45 and $49
- Test-retest errors? High tech computerized equipment resulting in little technician error = up to 40% improvement
- Technical Requirement? Innovative test equation is fully automated generating a four page report telling the client: Body fat percentage, lean mass, how they rank nationally among their age and gender peers, where they should be for health reasons, and how to get there.
- Lung Volume? Same formula as used by Johns Hopkins Hospital. This eliminates the cumbersome, costly, time consuming measuring of the residual lung volume.
The most common body fat test uses the skinfold caliper, a device that pinches your skin, pulling your fat away from your muscles and bones. You feel moderate discomfort, like when someone pinches your cheek. Typically the tester pinches three or four different sites on your body, such as your abdomen, arm, and back. The thickness of each pinch is plugged into a formula to determine your subcutaneous body fat level.
Many things can go wrong with a caliper test. The tester may not pinch exactly the right spot, or he may not pull all the fat away from the muscle. Or he may pinch too hard and accidentally yank some of your muscle. The calipers must exert a standard pressure and measure thickness to very small levels. Tests can vary greatly from tester to tester. Also, research shows that certain formulas are more accurate for certain ethnic groups, age ranges, and fitness levels.
Experts give this test a margin of error of four points, meaning your actual body fat percentage could be four points higher or lower than it actually is. Also tests show this test is accurate for about 90% of the population, when using the appropriate formulas. In laymen's terms, if you are one of the lucky 9 out of 10, and your body fat measures 12% - it could really be anywhere from 8% to 16%. If you are the one in 10 (for example you are very lean or your body fat exceeds 30%) then all bets are off We have seem errors run as high as 10%.
Because of the consistency in results, the high percentage of people that this test is successful for, and the low margin of error, this is generally accepted as the best field test, outside of clinical testing such as hydrostatic, DEXA, and MRI.
For Optimal Results in Skinfold Measuring, the following protocol must be followed:
All technicians must participate at a workshop where they spend considerable time learning the exact sites and technique and then after practice all participants actually do an interclass correlation on a minimum of 15 subjects to determine their test-retest reliability at each of the seven sites. Jackson-Pollack sum of 4 equations. They are also taught that the caliper must be Lange or Harpenden. Jackson found .98 inter-tester correlations, indicating that if I'm good (reliable) and you're good, then my measurement of an individual will be identical to yours. The workshops back this up by UWW. Depending on technique, obese individuals (>35%) can have skinfold tests done on them successfully. This assumes a two handed technique.
The problem lies in that very, very few technicians go to this extent to perfect their technique.
If you go with caliper testing, be sure to get tested before your work out. When you exercise, blood travels to your skin to cool you down. This can cause your skin to swell, and you may test fatter than you really are.
In 90% of the population, within +-4%
In 10% of the population errors are off the scale!
Derived result: based on hydrostatic comparison
Technical sources of error
Overestimate Lean, Underestimate Obese
Ethnicity Spec ific
Intratester/Test-Retest Error Prone
Cheap Calipers add significant deviation
Anthropometric measurement (girth and length) is a quick, easy and inexpensive method to estimate body composition. Using a standard calibrated cloth tape and a scale, your weight, height, and anywhere from two to four circumference comparisons are used to calculate your body fat. This test is based on the assumption that body fat is distributed at various sites on the body such as the waist, neck and thigh. Muscle tissue on the other hand is usually located at anatomical locations such as the biceps, forearm and calf.
There are a variety of formulas for this test, which vary excessively. The YMCA test has been shown to be very inaccurate, whereas the ARMY test compares favorably to skinfold testing in 89% of the population. It has been shown to be inaccurate for women above 40 years old, elderly and very lean. Circumference testing is used in the military due to ease of testing, low cost, relative accuracy, and lack of training requirement. When tests are marginal and are challenged, hydrostatic testing is normally used. One of the biggest weaknesses of this test is that most of the test data has not covered a wide enough spectrum of people in terms of obesity, racial types, and age variations, for each of the various methods used.
In 86% of the population, within +-5%
In 14% of the population, within 6-50%
Derived result: based on Hydrostatic comparison
Highly population dependent
Racial specific data is lacking
Wide variety of formulas
Inaccurate for middle aged women, elderly
Bioelectrical Impedance Analysis (BIA)
Another common method of body fat testing is bioelectrical impedance. You lie on your back while a signal travels from an electrode on your foot to an electrode on your hand. The slower the signal, the more fat you have, because fat impedes the signal.
BIA testing divides the body up into 'cylinders'. The arm, the torso, the upper leg, and the lower leg make up four separate cylinders for purposes of this test. The current flows through your body, finding varying resistance depending on the density of your muscle, the amount of body fat encountered, and the hydration of your tissue.
Bioelectrical impedance can have a huge margin of error, especially if you're extremely fat or extremely lean. In one study, world-class female distance runners averaged 20 percent body fat, when more reliable methods showed that they were closer to 10 percent. Dehydration also can skew the results; the signal slows down, and you appear to have more fat than you really do.
The following rules must be followed to give any credence to the tests:
* Abstain from eating and drinking within 4 hours of the test
* Avoid exercising within 12 hours of the test
* Void (urinate) completely prior to testing
* Do not drink alcohol within 48 hours of the test
* Avoid taking diuretics prior to testing unless instructed by your physician
If you follow all of these rules you can get a fairly accurate reading. Compared to other testing methods (circumference, skin-caliper) this is the least accurate field test. Unfortunately, past history has shown that the protocol rules aren't usually followed. Often the test administrators don't make the rules clear; they are misunderstood, or just not taken seriously. In which case a much greater than necessary amount of error creeps into the equation.
BIA can give a very consistent test-retest result when given back to back. But inconsistency in hydration, body fluids and intestinal content can result in high degree of variation from day to day. This makes this test far less suitable for repeated testing when measuring small changes in body fat level.
Be wary of studies sponsored by the BIA companies themselves, showing their devices to have accuracy levels close to hydrostatic. Studies by the NIH, ACSM, AHA, US NAVY, and numerous other independent bodies consistently give this test at least a 3% margin of error when the protocols are followed and confirm the test inaccuracies at the extremes of the body fat scale.
In 82% of population, within +-3%
In 18% of population, 4-20% error
Derived result: based on Hydrostatic comparison
Proprietary population dependent formulae
Higher standard error range than other tests
Vastly overestimate lean, inaccurate among obese
Hydration, skin-temp, test condition compound error
Inaccurate for small changes
Additional Problems related to BIA
There are several BIA methods out there. One is a scale you stand on and the electrical resistance is measured up one leg and down the other. Then a formula with an assumption related to all the fat vs. lean mass above the pelvic is added and the resulting number is displayed. Another is a device you hold at arms length. Again, the resistance is up one arm and down the other. The another assumptive formula related to all fat and lean mass below the shoulders is factored into the scenario and viola’, your body fat percentage is displayed.
Near infrared uses light to measure fat through reflection. A device is pressed against your arm, and a single reading estimates your body fat. This method of assessing body fat is based on the principles of light absorption, reflectance, and near infrared spectroscopy. A computerized spectrophotometer that has a scan and probe are used. The probe is placed onto the biceps; it emits an infrared light which passes through both fat and muscle and is reflected back to the probe. Subject data such as height, weight, sex, age, frame size and activity level are taken into consideration. Density measurements are obtained and incorporated into the manufacturers proprietary prediction equations. There is currently only one NIR device on the market.
There are few studies on this device. The best known showed Near Infrared testing to be reasonably accurate for the norm and very consistent from test to test. It is also probably the easiest and fastest test of all. The study did show NIR to be consistently inaccurate for the two ends of the weight spectrum, the lean and the obese.
In test, immediate re-test comparisons using several technicians on the same subject, it is observed that technique is very important in getting a consistent reading. This requirement for high technician skill level makes this method less than reliable in anything other than a clinical environment.
Few validating studies
Insufficient corroborating data
Derived result: based on Hydrostatic comparison
Single point test considered inadequate
Underestimated >4% in obese (>30% fat)
Overestimated >4% in lean (8%-12% fat)
Body Mass Index (BMI)
Body Mass Index (BMI)Body Mass Index is often used to quantify an individual's obesity level. This is the simplest of tests - your height squared, divided by your weight. The result is looked up on a table. Only an individual's height and weight are used and no indication of actual lean or fat mass can be determined. This test takes no body composition information into account, and is simply an average based on population studies.
Originally, the body mass index was intended to be a broad indication of general health, but it often is used to determine cardiovascular risk. An indirect measure of body fat using height and weight, BMI can be determined by plugging in your height and weight on the U.S. Centers for Disease Control and Prevention's Web site (www.cdc.gov). (Type BMI calculator into the search engine.) For adults, a figure of less than 18.5 is considered underweight, while 18.5 to 24.9 is normal. If your BMI is 25 to 29.9 you're technically overweight, and anything over 30 is categorized as obese. For children, the interpretation of BMI is far less straightforward and varies by age and sex.
Researchers from the Mayo Clinic are now saying the BMI is just too blunt to be trusted. A study found that patients with a low BMI had a higher risk of death from heart disease than those with normal BMI, according to the research published in the Aug. 19 issue of The Lancet. At the same time overweight patients had better survival rates and fewer heart problems than those with a normal BMI. Also, since BMI can't differentiate between body fat and muscle mass highly trained athletes can have a high BMI and not be overweight. An extreme example is that in his prime, as Mr. Universe, Arnold Schwarzenegger's BMI was 33. That's not just overweight but obese.
Cannot determine fat mass
Only valid for broadest interpretation
No body composition allowance
High muscle density results in 20%+ error
Other Testing Methods that are generally not found to be portable or in the field.
There are several other methods of testing available. They are less frequently available and are not considered "field testing apparatus."
DEXA testing (Dual Energy X-Ray Absorptiometry) is very accurate and fast but very expensive. It does provide more accurate measurements of fat free mass. It is often combined with hydrostatic to get clinical accuracy. It tends to be very expensive, has low availability, and usually requires a licensed medical technician to operate. The test is very quick, under 20 minutes, but getting an appointment and time-slot can take weeks. Also, since this method requires a whole body x-ray a physician's referral is needed.
Air Displacement Plethysmography (ADP) (The Bod Pod) is similar to hydrostatic weighing, except it uses air displacement instead of water. It is a can be a close second to hydrostatic testing when available, and when conducted in a controlled environment. It is relatively fast and easy to perform. It is usually expensive. In field comparisons we have found a good deal of discrepancy between the Bod Pod and underwater weighing (UWW). We assume it is because of the humidity and barometric pressure variations found in the field that are not found in a clinical environment. Most of the studies (that we have found) which show an accuracy close to UWW, were funded by the company that manufactures the Bod Pod. Most independent studies show it to be off in both ends of the spectrum. Most reports we have read show the clients body fat percentage to be higher than expected.
Whole Body Gamma Counter (WBD) combined with In Vivo Neutron Activation Analysis (IVNAA) uses very complex lab equipment to capture gamma rays emitted by a subject. The gammas come from a naturally occurring isotope of potassium found in the human body. Total body potassium is an accurate index of the mass of metabolically active tissues in the body, and can be used with DEXA to continue refining the ability to accurately account for variations in fat free mass.
Whole Body Gamma Counter (WBD) combined with uses very complex lab equipment to capture gamma rays emitted by a subject. The gammas come from a naturally occurring isotope of potassium found in the human body. Total body potassium is an accurate index of the mass of metabolically active tissues in the body, and can be used with DEXA to continue refining the ability to accurately account for variations in fat free mass.
The Total Body Electrical Conductivity (TOBEC) machine consists of a cylinder that is open at both ends. It generates a very weak magnetic field produced with electric energy. As a subject passes through the cylinder, the strength of the magnetic field is altered in relation to the electrolytes found in the body water. Body water is a constant proportion of lean tissue, so this reading enables scientists to estimate lean body mass. The machine consists of a cylinder that is open at both ends.It generates a very weak magnetic field produced with electric energy. As a subject passes through the cylinder, the strength of the magnetic field is altered in relation to the electrolytes found in the body water. Body water is a constant proportion of lean tissue, so this reading enables scientists to estimate lean body mass.
MRI, Computed Tomography (CT), and Isotope Dilution can also be very accurate but are purely clinical, used in research, and are generally not used due to cost.